The invention relates to microelectronic semiconductor device assembly wafer bumping processes and specifically to the fabrication of a new under bump metallization (UBM) structure.
Current and future microelectronic interconnect packaging technologies involve solder bump interconnect bumping on copper wafers. Currently, wafer vendors provide aluminum capping of copper pads in the wafer bumping process, as well as, in wire bonding. Known bumping processes in plating technology will have UBM sputtered and patterned before forming the bump on the I/O pad. The present invention relates to a novel manufacturing process of a new under bump structure (UBM) as related to the manufacture of electronic components.
U.S. Pat. No. 6,268,114 B1 to Wen et al. describes a method for forming fine-pitched solder bumps/balls and devices formed by such method.
U.S. Pat. No. 6,222,279 B1 to Mis et al. describes a method for fabricating solder bumps on a microelectronic device having contact pads including the steps of depositing a titanium barrier layer on the device, forming an under bump metallurgy layer on the titanium barrier layer, and forming one or more solder bumps on the under bump metallurgy layer.
U.S. Pat. No. 6,130,141 to Degani et al. describes techniques for applying under bump metallization for solder bump interconnections on IC chips with Al bonding sites.
U.S. Pat. No. 6,153,503 to Lin et al. describes a process for producing solder bumps on metal electrodes, of a semiconductor wafer, which involves the formation of the under bump metallurgies on the electrodes.
U.S. Pat. No. 6,107,180 to Munroe et al. describes a method for forming an interconnect bump structure. Under bump metallization structure comprising a chrome layer, a copper layer, and a tin layer is disclosed.
U.S. Pat. No. 5,486,282 to Datta et al. describes a tool and process for electroetching metal films on a substrate employing a linear electrode and a linear jet of electrolyte squirted from the electrode.
It is therefore an object of the present invention to provide a process for the fabrication of a new UBM structure.
It is another object of invention to provide aluminum cap protection without using silicon nitride (SiN) passivation or benzocyclobutene (BCB), or polyimide (P1) repassivation, to prevent damage or undercut by etching solutions.
In order to accomplish these and other objects of the invention, it has been discovered that two UBM mask processes are utilized in the following manner:
First, a top layer of copper (Cu) is patterned and/or a middle layer of nickel-vanadium (NiV) or chrome-copper (CrCu) is personalized by standard photoprocessing and etching steps utilizing a bump based size mask. This is followed by a patterning seed layer step with a second, larger mask, thereby preventing damage to the aluminum cap and seed layer undercut during the etching process.